Current supply apparatus



Nov. 25, 19 2 F. w. ANDERSON CURRENT SUPPLY APPARATUS Filed Aug. 19,1949 LOAD CONTROLLED CIRCUIT a 5 c a 3 2 w m SIGNAL INPUT LOAD INVENTORFREOfR/C M44175? 44 05/290 AMP.

ATTORNEY Patented Nov. 25, 1952 CURRENT SUPPLY APPARATUS Frederic Vi.Anderson, Lynbrook, N. Y., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationAugust 19, 1949, Serial No. 111,208

2 Claims.

This invention relates generally to a regulatory system, and moreparticularly, to a regulatory system for controlling power supplyapparatus in accordance with one or the output parameters of the supply.

In certain types of communication systems, means must be provided toobtain a source of direct current power having a characteristic ofconstant voltage or current. Such direct current power may be requiredfor the charging of batteries, for the operation of repeater stationsand for many other purposes incidental to the field of communication.

According to the invention, a full wave, variable resistance network isemployed. This network is caused to vary in magnitude by means of acontrol signal of moderate or low power applied to the control grids ofthermionic discharge tubes included as part of the network.

One circuit, according to the invention, includes the variableresistance network as part of a phase shift bridge for grid-controllinga gaseous thermionic discharge rectifier power supply. Such gaseousthermionic discharge rectifiers may be of the type generally known as athyratron. By varying the resistance of the network in accordance with asignal derived from one of the output parameters of the thyratronrectifier, the control grid of the thyratron rectifiers may be shiftedin phase with respect to its anode voltage to provide an output having adesired constant current or voltage characteristic. The variableresistance network is shown with regard to another circuit, according tothe invention, controlling the alternating current input voltage of aconventional rectifier system in accordance with a predetermined outputcurrent or voltage. The main object of the invention is to provide afull wave, variable resistance network, arranged to control the outputof alternating current regu lator and rectifying circuits.

Fig. 1 shows a schematic electric diagram of a variable resistancenetwork in accordance with the invention;

Fig. 2 shows a schematic electric diagram of a preferred embodiment ofthe invention wherein a variable resistance network as shown in Fig. 1is emp oyed;

Fig. 2a shows an electric schematic variation applicable to the circuitof Fig. 2; and

Fig. 3 shows a further embodiment of the invention.

Referring now to Fig. l, a variable resistance network according to theinvention is shown to the left of the dotted line. A signal,representative of some condition to be controlled, is derived at signalinput I. This signal will ordinarily be a unidirectional voltage,varying in magnitude with the control to be effected. The signal issupplied in multiple to the grids of two thermionic discharge tubes 2and 3. The cathodes of the thermionic discharge tubes 2 and 3 areconnected together. Two unidirectional conductors 4 and 5 are connectedtogether in series opposition and the series combination is connectedbetween the anodes of the two thermionic discharge tubes 2 and 3. Thecommon cathode connection of tubes 2 and 3. is connected in turn to thejunction of the unidirectional conductors 4 and 5. The anodes of tubes 2and 3 are individually connected to the circuit 6 under control; inseries with the connection from one anode to the control circuit 6 is asource of alternating current 1.

The general plan will be to modulate the source of alternating current Iby the variable resistance network as it is supplied to the controlledcircuit 6.

In all discussions herein, the fiow of current will be assumed aselectron flow from negative to positive potential, as compared withconventional battery cur-rent flOW from positive to negative.

Unidirectional conductors and 5 are sometimes called varistors. They maybe metallic or disc rectifiers as shown, utilizing semiconductivematerials such as selenium or copper oxide; diodes or otherunidirectional conductors may also be employed. Varistor t will offervery high resistance to the passage of current flowing from a to b. Thelimit of this resistance is dependent upon the practical limitations ofthe unidirectional conductor employed. Conversely, little or noresistance is offered to current flowing from b to depending also on thepractical limitations of the unidirectional conductor employed.Similarly with varistor 5, a high resistance to the flow or" currentwill be experienced by current attempting to flow from a to 0; but a lowresistance will be experienced by current passing from c to a.

Current will flow from the alternating source I and in one branch path,passing from the source through the controlled circuit 6, to the point0. Assume that the source of alternating current 7 has at a giveninstant an output po1arity making the point D negative with respect toc, this polarity extending over a half cycle of the output of thealternating supply '3. The current at the now ne ative point i) will beunable to pass over the electron path of thermionic discharge tube 2.However, a low resistance current path is offered from b to a throughvaristor 4, to the oathode of tube 3, over the space charge path of thistube to the anode, and thence to positive point 0.

On the succeeding half cycle of the alternating supply 1, the relativepolarities of b to will have been interchanged. The voltage existing atpoint 0, now negative, will be unable to travel over the electron pathof tube 3. However, a low resistance current path is offered from c toa; the current will travel through the varistor to the cathode of tube2, over the electron path of this tube from the cathode to anode, thenceto positive point I).

When the current from the alternating supply 1' reaches that point inthe network where passage is made from the cathode to the anode of thethermionic discharge tubes 2 and 3, an apparent resistance will beinserted in the path between the cathode and anode, known generally asanode resistance. The amount of the anode resistance presented willdepend upon the potential of the individual control grids with respectto the cathodes. As the control grid of either one of the thermionicdischarge tubes becomes charged more negatively with respect to itscathode, the electron flow between the cathode and anode of thatdischarge tube will decrease in accordance with the negative increase incontrol grid voltage. Thus, the amount of resistance to the passage ofcurrent in either direction from point D to point 0 will depend upon thecontrol grid-cathode voltage of the thermionic discharge tube throughwhich the current flows. As the current from alternating supply 7 willflow successively through discharge tubes 2 and 3, the amount ofresistance inserted by these discharge tubes can be made to depend uponthe control grid-cathode voltage derived from signal input i. If leadl-a becomes more negative with respect to lead [-13, the anoderesistance of discharge tubes 2 and S and therefore the insertionresistance of the network on the left-hand side of the dotted line willbe increased. If lead l-a becomes more positive with respect to leadl-b, the anode resistance of discharge tubes 2 and 3 and therefore theinsertion resistance of the network will be decreased. If the signalobtained from signal input I is representative of a characteristicdesired at the input of the controlled circuit 6, the amount ofresistance inserted by the network including discharge tubes 2 and 3 canbe regulated to assist in maintaining the desired characteristic. Ifthermionic discharge tubes 2 and 3 are pentode vacuum tubes, a highercircuit resistance can be obtained than with triodes.

Referring now to Fig. 2, a thyratron power supply is here shownemploying a variable resistance network as previously described. Therectifier circuit compares in some respects with copending United Statesapplication of J. R. Stone, Serial No. 111,199, filed August 19, 1949,now Patent No. 2,592,615. The network here comprises two thermionicdischarge tubes !6 and I1; varistors l5 and I8 operate in the mannerdescribed with reference to Fig. 1.

In general, the circuit shown in Fig. 2 supplies a direct current to aload l2, from a prime source of alternating current, at terminals 8 and9. The alternating current is applied to the primaries of transformersi0 and H. The secondary of transformer It] provides a voltage to theanodes of full wave thyratron rectifiers l3 and Id. The thyratron outputis supplied to the load I2 with the negative lead from the center tap ofthe secondary of transformer 10 and the positive lead from the cathodesof thyratron rectifiers l3 and Control grid thyratrons or gas triodessuch as [3 and I 4 provide a variable output in accordance with thephase of their control grid-cathode voltage with respect to theanode-cathode voltage. The grid-electrode of thyratrons is able only toinitiate the flow of anode-cathode current; once this current flows, thecurrent magnitude is not controlled by the control grid nor is this gridable to stop the flow of current. Current will cease flowing when theanode voltage applied to the particular thyratron returns from apositive to the zero value and over the succeeding half cycle ofanode-cathode voltage presented from the secondary of transformer It].By delaying the control grid of the thyratron from reaching the pointwhere anode current may flow for an appropriate time, the total currentpassed by the thyratron anodes can be controlled. The problem ofcontrolling the output of thyratron rectifiers l3 and I4 is thereforereduced to one of shifting the phase of control grid-cathode voltagesupplied to the thyratrons with respect to the anode-cathode voltage, toobtain the desired constant current or voltage output.

When the control grid-cathode voltage is in phase with the anode-cathodevoltage, the output of the thyratron rectifiers will be at a maximum;when the latter two voltages are degrees out of phase, the output of thethyratrons will be substantially equal to zero.

To provide the desired shift in phase, a bridge circuit is employed,having as its four arms: the portion of the secondary of transformer llbetween points (1 and e; and between points 6 and j; capacitance 20; andthe full wave, variable resistance network between points I) and c. Atransformer l9 has its primary winding connected between vertices b ande of this bridge. The secondary of transformer 19 is center-tapped; theextremities of this winding are connected to the control grids ofthyratrons l3 and I4, the center tap being connected in multiple to thecathodes of these thyratrons.

That arm of the bridg between points I) and c, the variable resistancenetwork, operates in the manner described with reference to Fig. l.Thermionic discharge tubes i6 and H will provide successive paths ofvariable resistance upon the consecutive half cycles of the voltageprovided across points 2 and f of the transformer ll secondary. Theamount of the resistance inserted by the variable resistance networkdepends upon the control grid-cathode voltage applied to tubes i8 andIT; the resistance in the arm of the bridge extending from b to 0 willbe varied in accordance with changes of the latter voltage.

The primary winding of transformer 59, between and 6, will have avoltage adduced therein depending upon the voltage balance of the ridgearms. A voltage is developed across the arms from d to e and from g to,f of the secondary of transformer I I. The phase of the voltagepresented between b and e of the primary of transformer 19 will dependupon the magnitude of the variable resistance network between points band c. The balance obtained by the bridge circuit will depend upon themagnitude of this variable resistance and two extreme cases can beconsidered: (A) where the variable resistance network presents aresistance so high as to approach an open circuit, and (B) where themagnitude of the variable resistance network becomes so small as to benegligible. In the former case (A), the voltage presented by thesecondary of transformer l I between 6 and f can be virtually eliminatedfrom consideration, and the voltage presented to the primary oftransformer is is that developed across the d to'e portion of thesecondary of transformer I I in series with th capacitance 2G. The phaseof the voltage appearing across the primary of transformer is will beshifted 180 degrees from the supply voltage presented between terminals8 and 9. Assuming the second condition (B) the voltage at the primary oftransformer H! between b and e will be substantially th same voltage asexists between points e and of the secondary of transformer i l thevalue of resistance between points I) and will reach sucha' low value asto become negligible. The voltag then presented to the secondarytransformer I?! will be substantially the same voltage as exists betweenthe anodes of thyratrons l3 and [4. In the range between th twoconditions stated, for various values of the variable resistance networkin the bridge arm between points 19 and c, the voltage from b to e atthe primary of transformer 19 will vary from 180 degrees out of phase tothe iii-phase condition depending upon the value of the magnitud of thevariable resistance network bridge arm. The control of phase of thegrid-cathode voltage of thyratrons i3 and M can be obtained bymanipulating the ratio of the in and out-ofphase voltage componentssupplied the primary of transformer H3 in the manner described; thesecomponents being ultimately applied to the control grid-cathode circuitsof thyratrcns i3 and M through the secondary of transformer id.

The amount of phase shift in the thyratron grid voltage has been seen todepend upon the magnitude of the variable resistance network between 0and b, and thus ultimately upon the control grid-cathode voltage ofthermionic discharge tubes l and ii.

Assuming that the output of the thyratron rectifier system is to displaya constant voltag characteristic, a voltage divider 2| is connected tothe rectifier output. A portion of the output voltage is sampled over asegment 2lc, of voltage divider 2 i; this portion will contain voltagevariations proportional to output voltage changes of the rectifiersystem. Assuming that switch 22 is closed to the left-hand position, thevoltage developed across a will be transmitted to leads 23.

To obtain a closely regulated output voltage, relatively small voltagevariations appear across conductors 23, representative of output voltagevariations. The variations are amplified and presented to the controlgrids of discharge tubes i and l l, which in turn provide control of thethyratrons is and E4 in accordance with the prior description. A directcoupled amplifier is employed to increase the sensitivity of theregulatory system, and is shown to the left or the dotted line, in Fig.2. Voltage variations developed across 2 5-64 are supplied between thecathode and control grid of a thermionic discharge amplifying tube 24,in series with a sourc of bias 25.

With the polarities indicated in Fig. 2, a negative grid bias must beintroduced at amplilying tube 2 1, overcoming the residual positivevoltage developed at the upper end of 2 l-a which would render the gridexcessively positive; at the same time, th signals representative ofvoltage variation will be transmitted to the grid circuit of amplifier24. While bias supply 5 is indicated as a battery, any conventional typeof direct current power supply of suitable voltage stability may beemployed between terminals at-:c. Referring to Fig. 2a, a rectifier typepower supply, employing a regulatory gaseous discharge tube 38 may beutilized. Alternating current supplied to transformer 39 is rectified bya bridge rectifier t) and thence supplied in parallel with theregulatory tube 38 to the terminals ;r.r.

The signals representative of voltage variation in the output ofthyratron rectifiers l3 and is will be amplified in th amplifying tube24. This amplified voltage appears across resistance ZG-a, which is inturn coupled to the control gridcathode circuit of the variableresistance network tubes l6 and IT. Direct coupled amplifying tube 24may be a triode of the type shown, or of any convenient type.Resistances 26-00 and 25-17 in the circuit of th variable resistancenetwork discharge tubes I6 and I! are inserted to limit the flow of gridcurrent in the latter tubes.

To demonstrate the operation of the circuit, it may be assumed that thevoltage across divider 2i rises; a proportional rise develops acrossZl-a of voltage divider 2|. This variation will be communicated to thecontrol grid-cathode circuit of amplifier tube 24 over conductors 23;the steady direct current component developed across 2l-a is overcome,at least in part, by the bias supply 25. The increase in output voltagerenders the control grid of amplifier tube 24 more positive or lessnegative and will increase the anode-cathode current drawn by theamplifier tube. In turn, the voltage drop across resistance ze-a, commonto the grid-cathode circuit of. tubes 56 and H, will be increased,providing a more negative volt-age to the grids of IE and H. A morenegative voltage between the grid and cathode of It and I1 will increasethe resistance offered between points I) and c by the variableresistance network. As has been shown, this change in the bridge armwill shift the phase of voltage presented the primary of transformer l lin turn producing an increased phase shift between the grid-cathodevoltage and anode-cathode voltage applied to thyratron rectifiers l3 andI4. The latter increased phase shift decreases the output of thethyratrons l3 and M, providing a lower output voltage and thus correctsfor the originally assumed increase in output voltage.

Similarly, a decrease in output voltage can be shown to provide anincrease in thyratron output through the regulatory system described.

If the output of the thyratron rectifier system is to be regulated in amanner providing a constant current output, independent of the loadimposed upon the rectifier, the switch 22 is made to its right-handcontact. Resistance 2'! is connected in series with the output of thethyratron rectifier to the load; the voltage drop experienced byresistance 27 will depend substantially upon the load current flowingtherein. As a result, the leads 23 connected across resistance 27 willrefiect voltage variations representative of variations in the loadcurrent of the thyratron rectifier. In turn, these variationsrepresentative of load current changes are supplied to the gridcathodecircuit of the direct coupled amplifier tube 2%. The variations will beamplified in amplifier tube and are presented to the gridcathode circuitof th variable resistance network tubes !6 and ll; appropriate changesin the phase of the grid voltage presented to the thyratron rectifiers I3 and it will be achieved. The output of the thyratron rectifiers l3 andM are in turn altered to control the output voltage and maintain theload current at a predetermined value. a

To illustrate the operation of the system in providin constant currentregulation, a rise in load current will be reflected by an increase inVoltage drop across resistance 21, making the grid of amplifier tube 24more positive or less negative. As in the illustration of the constantoutput voltage condition, the more positive condition of the grid ofamplifier tube 24 will ultimately result in a reduction in the output ofthyratrons l3 and I4, lowering the rectifier output voltage and thusreducing the load current, compensatin for the originally assumed loadcurrent rise.

Similarly, a drop in load current can be shown to provide an increase inthyratron rectifier output, increasing the output voltage and increasingthe load current, and compensating for the load current drop.

Thus, depending upon whether switch 22 is operated to left or right-handcontact, the output of the thyratron rectifier supply can be maintainedto have either a constant voltage or constant current output operatingcharacteristic.

Referring now to Fig. 3, a regulating system, accordin to the invention,is shown as applied to other types of rectified arrangements. A sourceof alternating current is supplied to terminals 28 and 29; thence inseries with a full wave, variable resistance network between points I)and c, to the primary of transformer 30. The secondary of transformer 33is connected to a full wave bridge rectifier 3|, the output vertices ofthe bridge rectifier 3! being coupled to a load circuit 32.

The operation of the full wave, variable resistance network betweenpoints and b is as described with reference to Fig. 1. Assuming thatswitch 33 is connected to the lower contact, voltage divider 34connected across the output vertices of rectifier 3i will provide aportion of the output voltage to conductors 35. Variations proportionalto change in output voltage are transmitted to an amplifier 36 which canbe similar in construction to the one employing tube 24 in Fig. 2. Theoutput of amplifier 36 provides a signal input controlling the operationof the variable resistance network. The network introduces a varyingresistance between points 0 and b, in turn varying the magnitude of thealternating voltage supplied to the primary transformer 30, inaccordance with variations in the output voltage. The latter outputvoltage m'ay thus be maintained at a substantially constant value.

Similarly, variations in output load current will produce correspondingvoltage drop variations across resistance 31. Assuming switch 33 is madeto its upper contact, this voltage in turn is amplified by the amplifier36 and thence supplied to the full wave, variable resistance network.

Again, the magnitude of the alternating voltage supplied from terminals28 and 29 to the primary of transformer 30 can be varied by changing theresistance inserted between 0 and b by the variable resistance networkin accordance with changes in load current. An appropriate compensationin the alternating supply voltage may thus be made to the input oftransformer 30 maintaining the output voltage at such values that theload current will remain substantially constant.

It is obvious that the scope of the invention is not limited to thespecific embodiments described, and that the invention may be employedin arrangements other than those given by way of example.

What is claimed is:

1. A power supply system comprising a first and a second grid-controlledgaseous discharge device each having a cathode, an anode and a grid,energizing circuits for supplying an alternating voltage of given phaseto the anode-cathode circuits of the said gaseous discharge devices inpush-pull, means for supplying a direct current from the said gaseousdischarge devices to a load circuit to set up a direct output voltage, aconstant output control circuit comprising, a transformer having primaryand secondary windings, the primary winding of the said transformerbeing connected to the said alternating supply source having a givenphase, a phase shifting bridge having output vertices, first and secondarms displaced about the said output vertices, said first and secondarms comprising half portions of the secondary of the said transformer,means to couple the output vertices of the said bridge to thegrid-cathode circuit of the said first and second gaseous dischargedevices in pushpull, the third and fourth arms of the said bridgedisplaced about the said output vertices, said thirdarm including acapacitance element and said fourth arm having first and second branchpaths each including a thermionic discharge tube having a cathode, grid,and anode and an asymmetrically conducting device connected in serieswith the anode-cathode circuit of the said thermionic discharge tube andhaving a concurrent polarity of current flow therewith, means to connectsaid first and second branch paths in parallel and conducting inopposite directions respectively, means for amplifying said directoutput voltage, and means to impress the said am plified direct outputvoltage in multiple to the grid-cathode circuits of the said thermionicdischarge tubes.

2. In combination, rectifying means comprising a first and a secondspace current device each having an anode, a cathode and a controlelectrode for supplying current from an alternating-current supplysource through the space current path of said devices to a load circuit,a phase shift bridge circuit comprising two parallel cur rent pathsconnecting the input vertices of said bridge, one of said parallel pathscomprising a first and a second impedance arm in series, the other ofsaid parallel paths comprising in series a third arm having a reactiveimpedance and a fourth arm having a variable resistive impedance, theoutput terminals of said bridge being the common terminal of said firstand second arms and the common terminal of said third and fourth arms,said fourth bridge arm comprising a third and a fourth space currentdevice of the vacuum type each having an anode, a cathode and a controlelectrode and a first and a second asymetrically conducting device eachhaving a resistance to current flow in one direction 'therethrough whichis much lower than its resistance to current fiow in the oppositedirection therethrough, the anodes of said third and fourth devicesbeing connected respectively to an output terminal and an input terminalof said bridge, said cathodes of said third and fourth devices beingconductively connected, said first asymmetrically conducting devicebeing connected across the anode-cathode path of said third device andhaving a relatively low resistance when the cathode of said third deviceis positive with 9 respect to its anode, said second asymmetricallyconducting device being connected across the anode-cathode path of saidfourth device and having a relatively low resistance when the cathode ofsaid fourth device is positive with respect to its anode, means forimpressing a voltage from said supply source across the input terminalsof said phase shift bridge, means for impressing a voltage from theoutput terminals of said bridge upon circuits connecting the controlelectrode and cathode of said first and second space current devicesrespectively, means for deriving a unidirectional voltage which variesin response to changes of current flow in said load circuit, and

means for impressing said derived voltage upon 15 a circuit connectingthe control electrode and 10 cathode of each of said third and fourthspace current devices.

FREDERIC W. ANDERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 10 Number Name Date 1,926,280 Griffith Sept. 12,1933 1,943,088 Power Jan. 9, 1934 1,954,682 Schmidt Apr. 10, 19342,273,586 Moyer Feb. 17, 1942 2,300,510 Kovalsky Nov, 3, 1942 2,504,834Hartwig Apr. 18, 1950

